The goal of this research is to understand the molecular mechanics of the interfacial activity of water-soluble lipolytic enzymes. A variety of physical techniques (primarily NMR spectroscopy, but also DSC, EM, SANS) combined with kinetic analyses will be used to investigate phospholipid interactions with phospholipase-A2 (Naja naja naja) and phospholipase-C (Bacillus cereus), and phospholipid/triglyceride interactions with porcine pancreatic lipase and colipase. Specific problems include the following: (i) How do phospholipid interfaces vary in different aggregate structures and are these variations relevant to phospholipase activity? (ii) What are the stoichiometry and properties of phospholipid binding to phospholipase-A2 and -C? (iii) Can a unified kinetic model be developed that quantitatively accounts for phospholipase rates toward substrate as monomers, micelles, detergent mixed micelles, and bilayer vesicles? (iv) Is surface/core partitioning of triglyceride in lecithin/triglyceride particles measurable, variable, and can it be correlated with lipase activity? Results should be generalizable to a wide range of lipid/protein systems.